A PVDF dynamic pressure gage

Technologies for manufacturing and poling the dynamic pressure gage based on ferroelectric polyvinylidene fluoride polymer are described. Results of theoretical and methodical investigations of the gage and pressure profiles measured with this gage behind the shock wave front in solids are presented.     

Calculation of the Interphase Heat and Mass Transfer in a Nozzle Spray Cone Taking into Account the Drag Crisis and the Heat- and Mass-Transfer Crisis

Theoretical Foundations of Chemical Engineering - Details of a numerical model and the results of calculation are presented for the interphase heat and mass transfer in the two-phase flow produced...     

Effect of oxygen adsorption on the conductivity of thin SnO2 films

The effect of oxygen adsorption on the conductivity of a thin homogeneous film of tin dioxide was studied. The concentration of free electrons in the film as a function of the partial oxygen pressure in the atmosphere is described using a model formulated within the framework of a flat band approximation. The results of calculations are compared to experimental data.     

Temperature variation of the current-voltage characteristics of thin-film gas sensors

Variation of the current-voltage (I-U) characteristics of thin-film gas sensors based on tin dioxide (SnO₂) in the presence of various gases has been studied in a range of working temperatures from 200 to 450°C. The experimental I-U curves are interpreted assuming that various forms of adsorbed oxygen species are present on the tin dioxide surface and that the adsorbed ions can migrate over the surface with different mobilities. Features of the observed phenomena can be used for selecting working temperatures at which an analysis of the I-U curves can provide a basis for the identification of various species adsorbed on the same sensor.     

Variation of the conductivity of a thin film of tin dioxide in response to stepwise gas sampling

Variation of the conductivity of a thin film of tin dioxide (SnO₂) in response to a stepwise change in the content of various impurities present in the gas phase has been studied in a broad range of concentrations. The experimental data are interpreted within the framework of the Roginskii-Elovich model of adsorption kinetics. A gas-pressure-independent parameter characterizing the sensor conductivity variation is established. Using the phenomenon under consideration, it is possible to identify adsorbed gas species.     

Feature-Based Sequence-to-Sequence Matching

This paper studies the problem of matching two unsynchronized video sequences of the same dynamic scene, recorded by different stationary uncalibrated video cameras. The matching is done both in time and in space, where the spatial matching can be modeled by a homography (for 2D scenarios) or by a fundamental matrix (for 3D scenarios). Our approach is based on matching space-time trajectories of moving objects, in contrast to matching interest points (e.g., corners), as done in regular feature-based image-to-image matching techniques. The sequences are matched in space and time by enforcing consistent matching of all points along corresponding space-time trajectories. By exploiting the dynamic properties of these space-time trajectories, we obtain sub-frame temporal correspondence (synchronization) between the two video sequences. Furthermore, using trajectories rather than feature-points significantly reduces the combinatorial complexity of the spatial point-matching problem when the search space is large. This benefit allows for matching information across sensors in situations which are extremely difficult when only image-to-image matching is used, including: (a) matching under large scale (zoom) differences, (b) very wide base-line matching, and (c) matching across different sensing modalities (e.g., IR and visible-light cameras). We show examples of recovering homographies and fundamental matrices under such conditions.     

Dependences of the Thermophysical Parameters of Activated Thermal-Emission Cathodes on the Current in a Stable Arc Discharge

The influence of electrical current (in the range 20–150 A) on the thermophysical characteristics of activated thermal cathodes (W + 2% ThO₂) in a freely glowing low-pressure argon arc is investigated. For the first time, the dependences of key cathode parameters, such as the heat flux at the electrode, the voltage equivalent of the heat, the specific erosion, and the distributions of the temperature and work function over the extension length of the cathode from the holder, are obtained. A nonmonotonic dependence of the specific erosion on the electrical current with a minimal level at 50–60 A is noted.